This is a really great question. The fun thing about population genetics, (as opposed to the more experimental fields in biology) is that we can actually enumerate the forces (mutation, selection and random drift) that are acting on our subject of inquiry (an antibiotic resistance gene in a population of bacteria). The phrase you'll want to google is "time to fixation", and there's some really elegant work on the subject (check out Kimura's 1962 paper "On the Probability of Fixation of Mutant Genes in a Population" http://www.physics.rutgers.edu/~morozov/677_f2017/Physics_67... ) . All of the theoretical results tend to be in generation time, not chronological time, but you get the idea

It is a bit more complex than that. You probably would want to look at particular genes, rather than populations of bacteria. As with horizontal gene transfer microbes readily exchange genetic material under environmental pressure.

And as I understand, there isn't much research on that - "a genetic document is rather mute" - https://www.nature.com/articles/s41599-019-0251-8

> what roughly is the half-life of antibiotic resistance in populations of bacteria?

That's almost certainly gene specific.

Think about human resistance to Malaria: there is a pretty strong downside.

There are probably other resistances humans have that don't really have an active downside aside from enlarging the genome.

Which does count as a downside, to be fair. The genome has a maximum size set by the mutation rate.

One of the most important questions. I have zero experience I'm speaking on, but my guess is they'd never completely die out. Unless every single strain of resistant bacteria were evolutionarily disadvantaged, it seems like a few or a number would stick around.

And that's all are needed to keep them around. I really hope the period of human history with anti-biotics wasn't a small window we got lucky enough to live in, because modern life will be very without it.

> One of the most important questions. I have zero experience I'm speaking on, but my guess is they'd never completely die out. Unless every single strain of resistant bacteria were evolutionarily disadvantaged, it seems like a few or a number would stick around.

Antibiotic resistance is made up of expensive and inefficient adaptions that tend to drop out of the gene pool when those particular selection pressures subside.

From what I've read, cycling antibiotics over time is purported to be one method of fighting resistance.